梁—板混合单元分析桥梁车致振动与噪声

Analysis of Train-induced Bridge Vibration and Noise Based on Beam-plate Hybrid Elements

在平截面的假定条件下,通过建立梁—板混合单元有限元模型,采用车—线—桥耦合振动分析得到桥梁高频振动响应,再采用声学边界元法分析桥梁结构噪声。以32 m混凝土简支箱梁为例,讨论了不同的梁—板混合模型对计算精度和效率的影响,并与现场试验结果进行对比。由此验证了:在梁—板混合有限元模型中,跨中板单元区域的长度取5倍以上梁高时,桥梁高频振动和结构噪声仿真值均能取得良好的精度,计算效率可提高70%左右。桥梁振动和结构噪声的峰值频率范围为40 Hz^80 Hz,在梁侧传播时具有一定的指向性。采用梁—板混合单元模型计算得到30 m范围内的结构噪声与全板单元模型计算结果基本一致,但在30 m范围外,前者的计算值要比后者小2 d B(Lin)左右。因而,梁—板混合单元模型可有助于提高桥梁车致振动和噪声分析的效率。

Computational efficiency is a bottleneck in calculating train-induced high-frequency bridge vibration and associatedstructure-borne noise. In this paper, based on the plane cross-section assumption, the beam-plate hybrid elementswere introduced and the train-track-bridge coupling finite element model was built for analyzing the high-frequency vibrationresponse of the bridge. Then, the acoustical boundary element method was used to compute the structure-borne noise.Taking a 32 m simply- supported box- girder as an example, the computational efficiency and accuracy were investigatedthrough different beam-plate combination models. A field test was also carried out for verification. Results show that if thelength of the plate-element region exceeds five times of the height of the girder, the computational efficiency can be raisedby 70 % without loss of accuracy in comparison with the conventional finite element analysis with plate elements. The dominantfrequency of bridge vibration and the associated noise is 40 Hz-80 Hz; the structure-borne noise has some directivityalong the side of the bridge; in the range beyond 30 m away from the bridge, the results of structure-borne noise calculatedby the beam-plate hybrid elements model agree with the whole plate elements model, and the noise level of the former is approximately2 dB（Lin） smaller than the latter. Hence, the beam-plate hybrid elements are helpful for raising the computationefficiency of bridge vibration and noise induced by trains.